Loudspeaker cone rim treatment



Dec. 9, 1958 F. A. MA'NLEY ETAL LOUDSPEAKER CONE RIM TREATMENT FiledMarch 11, 1955 FIG.

v RIM TERMINATION i M7 2o CONE STRUCTURE V I SIMULATING TRANSMISSIONLINE FIG. 2

FIG. 4

FIG. 5

FIG. 6

INVENTORS. FRED A. MANLEY PAUL W.A KERMAN ATTORNEY ,the cone material.

United States Patent LOUDSPEAKER CONE RIM TREATMENT Fred A. Manley,Irondequoit, and Paul W. Ankerman,

Rochester, N. Y., assignors, by mesne assignments, to General DynamicsCorporation, a corporation of Balm ware Application March 11, 1955,Serial N 0. 493,601

13 Claims. (Cl. 181-31) This invention relates to loudspeaker cones andmore particularly to means for treating a loudspeaker to reduceresistance which is similar to the distributed resistance of the conematerial, an inductance which corresponds .to the distributed mass ofthe cone material, and. a capacitance which represents the distributedcompliance of This transmission line is terminated by cementing the coneto its basket mounting at the rim, known as rim termination. The rimtermination actually represents the compliant material which is used toattach the cone to the speaker mounting frame or basket. The

transmission line then simulates a frequency discriminatory structureand the rim termination should therefore present its characteristicimpedance :in order to reduce reflection.

Certain attempts have been made to reduce reflection by various methodsof treating the cone rim. One method comprises attaching a compliantleather ring (such as carpincho) to the cone periphery, and thenattaching this leather in turn to the mounting frame or'basket. Anothermethod is by moulding several corrugations at the periphery of the coneadjacent to where it is attached to the mounting frame or basket. IStill another method includes the addition of supplemental compliance atthe cone rim, such as by cutting radial slots, ,for example.

Accordingly, it "is a primary object of the present invention to providea new and improved loudspeaker.

Another object of the present invention is to -provide a newandimprove'd means for treating loudspeaker cone I'lITlS.

In accordance with this invention, the abovecited objects areaccomplished bymeans of a compliant adhesive mixed with a massiveingredient which is applied adjacent the cone rim to provide adistributed resistance, mass, and compliance in proper width andthickness of application to terminate the loudspeaker cone by presentingapproximately its characteristic impedance. This treatment reduces themechanical reflection at the rim of the sound waves traveling in thepaper from the voice coil to provide more uniform sound radiation withrespect to frequency.

The invention, both as to its organization and method of operationtogether with further objects and advantages thereof, will be understoodbest by making reference to the following specifications taken inconnection with the accompanying drawing in which:

Fig. 1 illustrates a cross-sectional view of a typical loudspeaker;

Fig. 2 illustrates the electrical circuit which is equivalent to aloudspeaker;

Fig. 3 illustrates the application of a weighted comthe cone adjacentthe outer periphery thereof. -grooves may be of suitable configurationas concentric annular corrugations, for example.

the c one 22, and the compliance of the cone '23.

2,863,520 Patented, Dec. '9, 1-9558 pliant adhesive to the rim edge of aloudspeaker cone in accordance with the present invention; and

Figs. 4 through 6 illustrate alternative .methods .of

applying the weighted compliant adhesive.

Referring now more particularly to the drawings, there is illustrated inFig. 1 thereof, a cross-sectional view of 1 section, is generallyprovided near the apex of the cone and a second support 6 is providedfor attaching the cone to the basket at the outer edge'orrirn' thereof.

1 Elements Sand fi'thus cooperate to support the speaker cone. Element 6comprising grooves or rolls 7 provides means having predeterminedcompliance for supporting These In accordance with the presentinvention, as will be described in more detail hereinafter, a compliantmatefrial is added in these rolls in element 6 adjacent the outerperiphery or rim as is shown at 8 to provide a proper cone rimtermination.

A typical loudspeaker may be shown by ,an equivalent circuit as in Fig.2. The voice coil 20 is loaded acoustically by the resistance of thecome 21, themass of It will; be seen that these three elements provide afre- .quency .discriminatory circuit since the cone is loaded attheouterfperipheryby attachment tothe basket. This may be shownelectrically as rim termination 25. It

:will be seen ;that without this rim termination thelQud- .;speakerwould have resonance "at any frequency to which ,the discriminatorycircuit; may be :tuned. This generally .roccurs indhe -50 O to :1500:cycleregidn. By loadingrthe rim :periphery with; a suitablecompliantimaterialhaving relatively appreciable mass, the characteristic.impedance of ;the speaker is quiet at ,the; :rim :.termination:' andthe resonance disappears.

Several-methods -may be used to I provide; rim-.loadirig as.; by;.; acombination ;or;:mixtu re offloading: and holding materials uniformlydistributed :togterminate:zthe :cone

, at the; circumference thereof. iHoWeveL-i the embodiment ofthejnventiongshownfin the drawingsguses. aiholding material in the,form; of -a: suitable compliant @adhesive which isloaded;by; somenothercompoundshavingrehtively appreciable mass. l'Ihe Adhesive vehicle may.be

y" IW is ifiexib provided that :the. idegreej of. :flexibility is stablewith;,r,esp.ectstoaitimez{temperatureland humidity. For example, theadhesive which is made and sold under the name Geon 576 has been foundto have suitable characteristics. Any suitable mass ingredient, such aslead powder, for example, may be used. Other suitable mass ingredientscomprise lead oxide, mercuric oxide, fine sand, and the like. In thecase of a lead powder and Geon S76 mixture satisfactory for use on atypical 8 inch speaker, a proper speaker operation may be had where theproportions are one part by weight Geon 576 and one part by weight leadpowder 200 mesh.

It should be understood that the .preceding illustration of a mixturecomprising an adhesive and a loading compound is cited by way of exampleonly and that many flexible materials may be impregnated with a massiveingredient to provide a similar result.

It should be further understood that the preceding example of leadpowder 200 mesh is given by way of example only and that the massparticle size and compliance of the treated area will vary dependingupon the characteristics of each speaker. If the particles are maderelatively smaller, the mixture becomes more compact, stiffer and lesscompliant, since the distances between particles are smaller. On theother hand, the mixture becomes less compact, lighter per unit volume,and also more compliant, if the particles are relatively larger sincethe distances between the particles are greater. The compactness of themixture is selected according to the speaker requirements and relates tothe thickness and the amount of paper used in the cone. Hence, it isseen that the mass distribution of the mixture varies directly with themass distribution of the paper.

This mixture may be positioned in or applied to any of the grooves orrolls in the outer periphery of the speaker cone or combination thereofas illustrated in Figs. 3 through 6 by reference numerals 8a--8d,respectively. The proper weight, location and thickness of this materialdepends primarily upon the particular speaker being used.

The mixture is applied uniformly about the circumference of the speakercone. While many different methods of application may be used, it isfound that one suitable method comprises applying the mixture with apaint brush. Obviously, some of the loading ingredient may tend to movefrom the tops of the grooves or rolls to the bottoms thereof before theadhesive sets; however, these variations have been found to have littleeffect.

While We have described only a few embodiments of our invention, itshould be understood that various modifications thereof may be made.Therefore, we intend to claim all modifications that fall within thetrue spirit of our invention.

What is claimed is:

1. In a loudspeaker, a vibratile diaphragm having a predeterminedcompliance at the periphery thereof, means for supporting said diaphragmadjacent the outer periphery thereof, said means for supporting saiddiaphragm comprising means for providing a circumferentially anduniformly distributed mixture of a holding material and a loadingmaterial adjacent said periphery for determining the mechanical actionof said support, whereby said periphery is terminated by a substantialmass, said mix-' ture being such that said predetermined compliance remains unchanged.

2. The loudspeaker of claim 1 wherein said holding material comprises aflexible, adhesive vehicle and said loading material comprises a massiveingredient.

3. The loudspeaker of claim 2 wherein said massive ingredient is leadpowder.

4. The loudspeaker of claim 3 wherein said mixture of vehicle andmassive ingredient comprises equal proportions by weight of saidvehicle'and said lead powder.

5. The loudspeaker of claim 2 wherein said massive ingredient compriseslead oxide.

6. The loudspeaker of claim 2 wherein said massive ingredient comprisesmercuric oxide.

4 7. The loudspeaker of claim 2 wherein said massive ingredientcomprises fine sand.

8. A loudspeaker comprising vibratile means having a particular degreeof stiffness, means for supporting said vibratile means adjacent theouter periphery thereof, and

means comprising a mixture of a massive ingredient and a flexible,adhesive vehicle circumferentially and uniformly distributed adjacentsaid periphery, said ingredient comprising a plurality of particles, theflexibility of said adhesive vehicle being such that said particulardegree of stiffness is maintained.

9. The loudspeaker of claim 8 wherein said means for supporting saidvibratile means comprises a plurality of grooves formed adjacent saidouter periphery thereof, said mixture being applied adjacent theoutermost of said grooves.

10. The loudspeaker of claim 8 wherein said means for supporting saidvibratile means comprises a plurality of grooves formed adjacent saidouter periphery thereof, said mixture being applied on a plurality ofsaid grooves.

11. The loudspeaker of claim 8 wherein said means for supporting saidvibratile mean terminates in a plurality of rolls, said mixture beingapplied on an inner one of said rolls.

12. In a loudspeaker, means for vibrating a mass of air having acharacteristic rim termination, means having a predetermined compliancefor supporting said first named means adjacent the outer peripherythereof, and means for providing a substantially uniformly andcircumferentially distributed mass comprising a mixture of flexibleadhesive vehicle and particles of massive ingredient positioned adjacentsaid outer periphery, the size and weight of said massive ingredientparticles being determined by the nature of said rim termination andsaid predetermined compliance.

13. In a loudspeaker, means having a predetermined compliance at theperiphery thereof for vibrating a mass of air, means including saidperiphery for supporting said first named means, means comprising amixture of an adhesive vehicle and a finely divided massive ingredientcarried by said periphery, said mixture being such that saidpredetermined compliance remains unchanged, whereby said massiveingredient is distributed substantially uniformly and circumferentiallyadjacent said periphery.

References Cited in the file of this patent UNITED STATES PATENTS2,549,091 Hopkins Apr. 17, 1951 2,734,591 Olson et a1. Feb. 14, 1956FOREIGN PATENTS 237,699 Great Britain Aug. 6, 1925 293,414 Great BritainMar. 4, 1929 320,802 Great Britain Oct. 24, 1929 534,412 Germany Sept.26, 1931 596,893 Great Britain Jan. 13, 1948

